Magnetic separating device



Dec. 7, 1954 w, w, MOJDEN ETAL 2,696,301

MAGNETIC SEPARATING DEVICE 2 Sheets-Shet 1 Filed Dec. 2, 1949 IN VENTOR.

Ma 17mm: (1.1 b7 7 BY Me rsa/1 J. Ten ca;

Dec. 7, 1954 w, w, MQJDEN ET AL 2,696,301

MAGNETIC SEPARATING DEVICE Filed Dec. 2, 1949 2 Sheets-Sheet 2 IN VENTOR.

MAGNETIC SEPARATING DEVICE Wallace W. Mojden and Emerson J. Tenpas, ErieCounty, Pa., assignors to Eriez Manufacturing Company, Erie, Pa., acorporation of Pennsylvania Application December 2, 1949, Serial No.130,704

9 Claims. (Cl. 209-219) This invention relates generally to a magneticseparating device and more particularly to a method and apparatus forseparating extremely fine magnetizable powdered material from extremelyfine non-magnetizable powdered material.

The removal of fine iron from fine powders has been a challenge to themagnetic separation industry for some time. As powders become finer, thecohesive attraction of the particles for each other and most everythingelse increases. The powders tend to stick to the surface of a separatorsuch as a belt or drum, and be carried around and discharged with anyiron that may be attracted. In addition, the attraction of a magnet to aparticle of iron is in proportion to the mass of the particle of ironuntil the iron particle approaches one micron in size, when itsreluctance is increased many times. The separation difficulties can beappreciated when we realize that a magnet must attract a minute particleof iron from a cohesive mixture and must remain clean of the cohesive orsticky powder.

A major fault with all previous experimental devices has been the largeamount of non-magnetic material removed with the iron. Unsuccessfulexperimental devices utilized either an induced grid type magneticseparator or large and expensive magnetic induced roll types to overcomethe problem. The grid type was not selfvcleaning and was notcommercially acceptable. The induced roll separator was not successfuldue to the tendency for the powder to adhere to the rolls and be carriedaround with the iron. The induced roll type separator is large, heavy,and expensive. Iron particles do not leave the rolls, but accumulate,making manual cleaning necessary.

No magnetic separating device has heretofore been devised tosuccessfully separate extremely fine magnetizable material fromextremely fine non-magnetizable material. Even when it has been possibleto successfully attract the fine magnetizable particles, plugging upusually occurs, due to the reluctance of the nonmagnetizable particlesto separate from the magnetizable particles. It has also been difiicultto attract extremely fine magnetizable particles inasmuch as theattraction of a magnetizable material to a magnet is in proportion tothe mass of the magnetizable particle.

Because of the difliculty of attracting extremely fine magnetizableparticles, it has been necessary to expose them to a very strongmagnetic field which is best obtained at the edge of an air gap. Theamount of iron contamination contained in most fine materials is usuallyso great that a self-cleaning unit becomes imperative. Where a rotatingmagnetic drum has heretofore been used for separation of fine particledmaterial, it has been practically impossible to remove the magneticmaterial from the drum inasmuch as the non-magnetizable material sticksto the surface of the drum.

It is, accordingly, an object of our invention to overcome the above andother defects in present methods and apparatus for separating finemagnetizable particles from non-magnetizable particles and it is moreparticularly an object of our invention to provide apparatus forseparating fine magnetizable particles from nonmagnetizable particleswhich is simple in construction,

economical in cost, economical in manufacture, and efficient inoperation.

Another object of our invention is to provide novel magnetic means forseparating extremely fine magnetizable material from non-magnetizablematerial.

United States Patent Another object of our invention is to provide anovel method of separating extremely fine magnetizable material fromnon-magnetizable material.

Another object of our invention is to provide a rotatable magnetic drumor cylinder with novel means for removing magnetizable material gatheredon the face thereof.

Another object of our invention is to provide means for flowing finepowdered material onto the face of a revolving magnetic cylinder and anovel rotatable induction member associated therewith to remove themagnetizable particles in said powdered material from the face of saidcylinder after the non-magnetizable material is removed therefrom bycentrifugal force or grav- 1ty.

Another object of our invention is to provide a battle or baffles forre-enteriug the material to be separated onto the face of a rotatingmagnetic cylinder.

Another object of our invention is to provide means adjacent a magneticdrum for agitating the material and air adjacent to the face of thedrum.

Another object of our invention is to provide a novel combination andarrangement of parts in a magnetic separating device to separate finemagnetizable material from fine non-magnetizable material.

A more particular object of our invention is to provide a magneticseparating device embodying the following principles of operation:

1. To momentarily overcome the cohesive attraction of a powder byviolently and mechanically tearing the powder apart;

2. To momentarily speed up the movement of a powder to thin and stretchout the powder;

3. To have relative movement between a stretched gultd film of powderand a series of strong magnetic 4. To directly expose the pole pieces orgap edge (the point of maximum flux concentration) to the powder;

5. To magnetically attract and hold magnetic particles to the face of arapidly revolving cylinder and by centrifugal force throw off thenon-magnetic particles, keeping carry-over to a minimum;

6. To re-introduce the powder to a rapidly revolving cylinder by aseries of baffies for repeated combingd by a series of strong exposedmagnetic pole pieces; an

7. To automatically remove the iron from the surface of the cylindercontinuously and without wear to the cylinder.

Other objects of our invention will become evident from the followingdetailed description, taken in conjunction with the accompanyingdrawings, in which Fig. l is a side elevational view partly in sectionand more or less in diagrammatic form of our novel magnetic1 separatingdevice for extremely fine powdered materia Fig. 2 is an enlargeddiagrammatic side elevational view of a magnetic cylinder and there-entrant bafile and the cleaning drum associated therewith; and

Fig. 3 is a side elevational view of a modified form of re-entrantbafile for our novel magnetic separating device.

Referring now to the drawings, we show in Figs. 1 and 2 a rotatablecylinder 1 having banks of magnets 2, preferably U-shaped, spaced aroundthe internal periphery thereof and secured to the outer shell of thecylinder 1 by screw bolts 3. The U-shaped magnets 2 pro- .vide aprogressive series of magnetic fields running parallel to the axis ofthe cylinder 1. We show in Figs. 1 and 2 a cylinder 1 having fourU-shaped banks of magnets 2 spaced around the inner periphery thereofthereby providing eight magnetic fields; however, any suitable number ofmagnets maybe used. The cylinder 1 is preferably revolved at arelatively high speed compared with present magnetic drums or pulleys.The powdered material to be separated is introduced to the surface ofthe cylinder 1 from a chute 6 which is designed to slowly feed materialto the face of the cylinder 1 in a relatively fine even flow. The chute6 may have a bracket 7 attached thereto to, which is attached anarmature 8 disposed adjacent the outer face of the cylinder 1. Uponrotation of the cylinder 1, the changing magnetic fields of the magnets2 cause inward and outward movement of the armature 8 thereby causingvibration of the chute 6. Our device will operate extremely well withoutthe armature 8; however, in certain types of installations, it isdesirable to have such a device for vibrating the chute 6. Aconventional magnet (not shown) is preferably disposed in the feed linebefore the chute 6 to remove any tramp iron before entering the face ofthe cylinder 1 to prevent damage.

We provide an arcuate shaped re-entrant bafile 11 spaced from the outerface of the cylinder 1 with the distance between the baffle 11 and theface of the cylinder 1 gradually decreased from the entrance point ofthe material at the chute 6 to the lower end of the baffle 11. Thebat-He'll has inwardly curved portions 12 spaced around the peripherythereof to progressively redirect the direction of flow of materialthrown outwardly from the face of the cylinder 1 back into the face ofthe cylinder 1 several times as it passes around to the bottom sidethereof.

Adjacent the lower terminus of the baffle 11, we provide a member 13secured by a bracket 14 with the upper end thereof adjacent thecylinder 1. This causes the air adjacent the face of the cylinder 1 tobecome turbulent and the non-magnetizable material which adheres to thecylinder 1 is agitated and thrown from the cylinder 1 and it is caughtby the curved baffle 15 and passed to a chute 15a extending to a pointremote from the cylinder 1.

At a point more than three quarters of a turn from the chute 6 beyondthe baffle 15, we dispose a rapidly revolving cleaning drum 16 withlongitudinally extending, spaced, channel shaped members 17 secured byscrew bolts 18 on the periphery thereof. The drum 16 is mounted on ashaft 16a parallel to the shaft 80 upon which the cylinder 1 is mounted.The drum 16 may comprise a plurality of side by side relatively thindisks (not shown) with transversely bent, radially extending arms or anyother suitable magnetizable construction may be used to remove themagnetizable material from the face of the cylinder 1. The material usedin constructing the drum 16 is preferably non-magnetizable material inorder that the comparatively thin channel shaped members 17 adjacent theouter side or face of the cylinder 1 in the magnetic fields produced bythe magnets 2 will be magnetically induced as they approach the face ofthe cylinder 1 thereby causing all or a major portion of themagnetizable material on the face of the cylinder 1 to be attractedthereto and gathered thereon.

The thin section of the channel members 17 provides increased fluxconcentration. As the drum 16 revolves due to induced magnetism from thechanging rotating magnetic fields produced by the magnets 2, themagnetizable particles gathered on the channel shaped members 17 arecarried away from the face of the cylinder 1 and out of the magneticfields produced by the magnets 2 at which point the induced magnetism inthe members 17 will be greatly decreased, thereby lessening theattraction of the fine magnetic powdered material to the drum 16 and itwill be thrown into a chute 19 by centrifugal force or it will falltherein by gravity.

The cylinder 1 is rotated through a belt 21 and pulleys 22 and 23 on theshaft 80 of the cylinder 1 and shaft 24 of an electric motor 25,respectively.

In the operation of our novel separating device, the air gaps andtherefore the magnetic fields produced by the circumferentially spacedbanks of magnets 2 run parallel to the axis of the cylinder 1. Thecylinder 1 is preferably revolved at a high comparative speed. The finematerial to be separated is introduced to the upper surface of thecylinder 1 from the chute 6, preferably in a fine layer of uniformdepth. As the fine material strikes the outer face of the rapidlyrevolving cylinder 1, it will be immediately stretched out and thinnedout and torn apart because the centrifugal force throws the materialfrom the cylinder 1. This action exposes the magnetic particles in thematerial to be separated to the outer face of the cylinder 1. There is aslipping action or relative movement between the rapidly revolvingcylinder 1 and the material passing thereon from the chute 6. Thematerial never quite reaches the speed of the cylinder 1 so that we havecontinuous relative movement between the cylinder 1 and the material,causing the material to be combed by the series of magnetic fields.

The slipping magnetizable particles in the powdered material to beseparated pass directly over the strongest portion of the magneticfields produced by the banks of magnets 2 which is at the edge of theair gaps therebetween. The material thrown outwardly by centrifugalforce from the cylinder 1 strikes the inner face of the re-entrantbaffie 11 and the arcuate shaped curved surfaces 12 of the batlle 11cause the particles to progressively change their direction of flow andpass several times into the face of the cylinder 1 as the materialpasses around the face of the cylinder 1 through approximately one-halfa turn thereof. The material is repeatedly combed by the magnetic fieldsof the magnets 2 as it moves around the cylinder 1.

In the separation of certain materials, magnetic and non-magneticmaterial may be cohesively held together on the face of the cylinder 1after leaving the baffle 11. To overcome this, we have provided a member13 with the upper end thereof adjacent the cylinder 1 to causeturbulence of the boundary layer of air adjacent the face of therotating cylinder 1 whereby the material on the cylinder 1 is agitatedand the non-magnetizable particles leave the cylinder 1 and pass to thechute 15a by gravity or centrifugal force or both. The magnetizableparticles remain on the surface of the cylinder 1 attracted by the banksof magnets 2 until they reach the vicinity of the drum 16 which ismagnetized by induction from the banks of magnets 2 and which is rotatedby induced magnetism from the rotating magnetic fields of the banks ofmagnets 2 in the cylinder 1. The magnetic material remaining on the faceof the cylinder 1 will be attracted to the magnetized channel shapedmembers 17 of the drum 16 and they will be pulled away from the face ofthe cylinder 1. As the drum 16 revolves, the channel shaped members 17holding the magnetizable material gathered thereon will move out of themagnetic fields of the magnets 2 and the induced magnetism in thechannel members 17 will be decreased thereby lessening the attraction ofthe fine magnetic particles to the channel shaped members 17 to whichthey are attached, and the magnetizable particles will be thrown fromthe members 17 by centrifugal force or they will fall therefrom bygravity into the chute 19. The side of the drum 16 remote from thecylinder 1 is normally out of the magnetic fields of the banks ofmagnets 2, or at least the stronger portions thereof. Also, the magneticfields tend to shunt through the channel members 17 and the magneticmaterial attracted thereto adjacent to the cylinder 1 thereby lesseningthe induced magnetism at other points on the drum 16 more remote fromthe face of the cylinder 1. The comparatively thin iron channels 17 arenormally magnetically induced to saturation. A major part of the ironbeing held to the face of the cylinder 1 transfers to the high intensityedges of the channels 17. As the cylinder 1 revolves, the inducedchannels 17 revolve With it. As the channels 17 on the induced drum 16move away from the cylinder 1, they move out of the magnetic fieldsthereof, lose their induction, and the i1r9on is dropped or thrown intoa flanged discharge chute The drum 16 may take many different forms suchas a series of side by side disks with transversely offset arms on theouter side thereof, a unitary finned unit, or any other suitablemagnetizable construction.

In Fig. 3, we show a modified form of the re-entrant baffle 11 shown inFigs. 1 and 2. Re-entrant baffle 50 in Fig. 3 has arcuate shapedportions 51 progressively decreasing in length in the direction of therotation of the cylinder 52 and consequently the direction of thematerial on the face of the cylinder 52.

It will be evident from the foregoing description that we have provideda novel magnetic separating device for separating extremely finemagnetizable material from extremely fine non-magnetizable materialwherein the magnetizable material is exposed directly to the strongestportion of the magnetic field of a rotating magnetic cylinder, whereinnovel means are provided for separating the non-magnetic material fromthe magnetic material, wherein means are provided for progressivelyredirecting the flow of material back to the face of the cylinder,wherein means are provided for agitating the particles and air adjacentthe cylinder, and wherein an induction cleaning unit is provided forremoving the magnetizable material from the face of the cylinder rotatedby induced magnetism from the magnets of the magnetic cylinder.

Various changes may be made in the specific embodi ment of our inventionwithout departing from the spirit thereof or from the scope of theappended claims.

What we claim is: v

1. A magnetic separating device comprising a rotatable magnetic cylinderhaving spaced magnets around the periphery thereof, means for feedingmaterial to be separated into the face of said cylinder, and amagnetizable member disposed adjacent said cylinder at a point remotefrom the point wherein the material is fed onto said cylinder saidmagnetizable member being forced to rotate by the magnetism inducedtherein by the rotating magnetic field of said cylinder whereby saidmagnetizable member is magnetically coupled to said cylinder to removemagnetic material from the face of said cylinder, the portion of saidmagnetizable member remote from said cylinder being outside of theactive magnetic fields of said cylinder.

2. A magnetic separating device comprising a rotatable cylinder, magnetsdisposed around the inner periphery of said cylinder, a chute forfeeding material to be separated into the face of said cylinder, abafile extending from said chute to the underside of said cylinder andspaced from said cylinder having portions shaped to redirect the flow ofmaterial thrown from said cylinder back to the face thereof, and amagnetizable rotatable member having the outer side thereof adjacent theperiphery of said cylinder at a point remote from the point whereinmaterial is fed onto said cylinder for removing magnetic particles fromthe face of said cylinder, the portion of said magnetizable rotatablemember remote from said cylinder being outside of the active magneticfields of said magnets carried by said cylinder whereby magnetizablematerial will drop by gravity therefrom at a point remote from saidcylinder.

3. A magnetic separating device as set forth in claim 2 wherein thedistance between said baffie and said cylinder gecreases from the upperto the lower side of said cylin- 4. A magnetic separating device as setforth in claim 2 wherein the length of said shaped portions decreases inthe direction of rotation of said cylinder.

5. A magnetic separating device comprising a rotating magnetic cylinderhaving spaced magnetic fields around the periphery thereof, means forfeeding material to be separated into the face of said cylinder, abaffie spaced from said cylinder leading from the point where saidmaterial is fed onto the face of said cylinder a substantial distancearound said cylinder, and a magnetizable rotatable member disposedadjacent said cylinder at a point remote from the point on said cylinderwhere material is fed thereon and beyond the end of said baffie toremove magnetizable material from the face of said cylinder, the outerportion of said magnetizable rotatable member remote from said cylinderbeing without the active field of said magnetic cylinder saidmagnetizable member being rotatably actuated by the magnetic field ofsaid cylinder whereby the peripheral speed of said magnetizable memberis substantially equal to the peripheral speed of said cylinder.

6. A magnetic separating device comprising a rotatable magnetic cylinderhaving means to form spaced magnetic fields around the peripherythereof, means for feeding material to be separated onto the face ofsaid cylinder substantially normal thereto, an arcuate shaped baffiespaced from the outer side of said cylinder having arcuate shapedportions for re-entering the material passing from said cylinder intothe face of said cylinder, a radially extending member disposed adjacentthe periphery of said cylinder at the end of said baffle to agitate thematerial and air on the periphery of said cylinder, and means forseparately removing the magnetizable and non-magnetizable material fromsaid cylinder and means for receiving the non-magnetizable material,said means termi- Eating in a baifie spaced from said radially extendingmem- 7. A magnetic separating device as set forth in claim 6 wherein arotatable magnetizable member is disposed adjacent said cylinder at apoint remote from the point where said material is fed thereon to removemagnetizable particles from the face of said cylinder, the portion ofsaid rotatable magnetizable member remote from said cylinder beingdisposed outside of the active magnetic fields of said cylinder.

8. A magnetic separating device comprising a rotatable cylinder, magnetsdisposed around the inner periphery of said cylinder, a chute forfeeding material to be separated substantially normally into the face ofsaid cylinder, a rotatable magnetizable member adjacent said cylinderhaving the outer side thereof adjacent the periphery of said cylinder ata point remote from the point where material is fed onto said cylinderfor removing magnetic particles from the face of said cylinder, aportion of the outer side of said rotatable magnetizable member beingoutside of the active magnetic field of the magnets rotatable in saidcylinder, a bafiie leading from the point where material is fed ontosaid cylinder around a substantial portion of said cylinder and oppositeto said magnetizable member, and means on the inner side of said bafflefor re-entering material to said cylinder being thrown therefrom bycentrifugal force.

9. A magnetic separating device as set forth in claim 8 wherein saidchute has an armature secured thereto disposed in the magnetic fields ofsaid magnet whereby said chute is vibrated upon rotation of saidmagnets.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 148,517 Smith Mar. 10, 1874 336,402 Fisher Feb. 16, 1886455,808 Wenstrom July 14, 1891 456,507 Fiske July 21, 1891 468,540 CaneFeb. 9, 1892 478,551 Ball July 12, 1892 487,073 Lovett Nov. 29, 1892832,823 Wait Oct. 9, 1906 939,523 Ludwick Nov. 9, 1909 1,141,833 SalwenJune 1, 1915 1,233,804 Pike July 17, 1917 2,326,575 Stearns Aug. 10,1943 2,410,601 Crockett Nov. 5, 1946 FOREIGN PATENTS Number Country Date38,367 Sweden Jan. 28, 1913

